Scientists have coaxed so-called stem cells to change into liver cells and used them to repair the livers of mice.

This experiment adds to a growing body of evidence that stem cells might be used to transform many aspects of medicine and research.

Stem cells are sometimes described as master cells because they can develop into different kinds of tissue in the body.

Scientists hope to use them in rejection-free tissue transplants as well as to study the fundamentals of cell development.

Cell changes

In a report to the annual meeting of the Society for Experimental Biology, held in San Diego, California, scientists from StemCells California Inc, a subsidiary of CytoTherapeutics Inc, announced that they have managed to produce mature liver cells from blood stem cells in mice.

"There have been two parts to our study so far," explained Dr Eric Lagasse of StemCells Inc. "In the first set of experiments, our collaborators from the Oregon Health Sciences University injected a group of mice undergoing liver failure with bone marrow cells."

The scientists found that the blood stem cells transformed themselves into another kind of cell altogether - a working liver cell.

"They found that this led to the restoration of liver functions, as measured by liver enzyme levels," said Dr Lagasse. Four out of the nine mice who had had their livers damaged survived.

Liver disorders

In a second series of experiments, the scientists demonstrated that transplanting as few as 50 blood stem cells can produce mature working liver cells.

Dr Lagasse added: "To our knowledge, this is the first time that restoration of liver function has been demonstrated after treatment with blood stem cells."

Scientists say that this discovery could open the way to use blood stem cells to replace or repair diseased or damaged tissue in a patient with liver disorders."

If they can get the technique to work in humans, it could provide a ready source of stem cells for liver cell therapy.

It also creates the possibility that the problems of tissue rejection that plague transplant recipients can be overcome by using the same cells to give rise to both the blood system and the liver system.

In addition, it may also open the way to better understanding the properties of the blood stem cells and how they might be manipulated to treat a variety of diseases.